Pistons - 351 crank, 302 rods

[MNTL.XD 3,831]

it really depends on  lot of things,id say 290rwhp isnt impossible ,i mean the gtho,p3 that did the 1,4 run back in its day only had 300hp and cracked 14,1,

 

you are going to run into detonation problems bc the old skool closed chamber heads cause it ,

 

with super led fuels we could get away with higher comps as we had led to lube the valves,or run av gas ,but the fuel today is shit as 98 hi octane burns slower ,and dumbs down the out put of the motor and it also causes a longer burn ratio for fuel to air

95  with octane booster is much better ,but the octane isnt in it

LPG  today is a mix of many diff gases and still doesnt give the octane it used to yurs ago ,

either way unless you have a plane ,to get av gas its gunna ping

Yeah, been told all that, he said he'd bought the ratio down to 10.5 because of that reason, reckons he's been doing Clevo's for years, i haven't so i just have to take his word for it. (Atleast i have a warranty with this engine, might come in handy. lol) I used to run the XD on a mix of premium and Av gas, but i think they have tightened the laws on it now so i'm not 100% sure if i'll still be able to get it. I used to go out the aerodrome to get it, but i had to fill a container, then pour it into the car. Will have to see if i can still get onto it through him. It will be getting started, ran in and tuned on the dyno when i've fitted it, so hopefully they tune it well. 

[gerg 10,871]

I know it's not quite the same, but my little 302 runs a mild cam and uses closed heads, can tolerate about 45 deg of timing on E10, I've heard some accounts of closed chamber actually being more efficient due to the quench area creating more turbulence, eliminating dead spots and reducing detonation that way

[FORD_MAN 1,026]

Hypertec 351 with 302C Rod pistons are also avalible as Forged pistons

[MNTL.XD 3,831]

I'm pretty sure Keith Black also do a piston to suit 351 crank/302 rod combo.

[PRO250 1,506]

i had a 351 built using 4mab crank 02 rods short skirt racing piston a stage 3 competition cam 460 valves in open chamber heads ,not throtted,it ran a 780 holley extractors ,t5 box 345lsd in an EA the most it did on the dyno ,was 290rwhp,and this thing went like shit off a shovel,lol 450 asking a little to much imo!

YOU  will find the compresson with close chamber heads is more like 13to 1, and itl ping like a bitch ,i have a mate with the same combo as you ,its fucked and pings everywhere

 

 

 

this build combo is called a 383 stroker!

Am i reading it right a 351 crank and 302 rods is a 383 stroker? cause its not its a 6inch rod clevo still a 351 just with a 6inch rod

[bear351c 10,270]

No. In order to be a 'stroker' the crankshaft has to be 'stroked'.  The offset of the journals is increased or decreased, from the centre of the crank.

[CHESTNUTXE 7,304]

how do you work out the compression ratio with the 6 inch rod combo ? with closed or open chamber heads

[SMIKXF / YEABRA 396]

Hey Chris,

 

I to am using this same combo the issues you will have as I didn't presumably you only want a mild street cruise engine, is compression ratio using 302 64cc close chamber heads will be way to high even if you dont deck the block and run dish pistons ( the biggest available) there is not enough crown to spin the piston down due to the high pin hight your cr would be about 12.9 to much for pump and cruise, I now have a set of 351 2v open chamber heads with 4v valves fitted, running it decked with slightly dished piston say 8cc gives me around 10.9 excellent for mild cam and 98 juice

 

So all in all its probs best to do a little research on the 302 head but thats just my seeing.

 

I have a mate that spent a reasonable amount of money on a set of 302 heads for his 351 and it went pretty well, he put a stock set of 351 2v on it with v4 valves went off its head.

 

I've had the exact same set up for my 351' n built it in 2005 and havng had an issue at all ! Made 340rw hp n goes pretty hard with top loader ,9' and 750dp on it

[CHESTNUTXE 7,304]

The cr with 58cc closed chamber heads on a std 351 unmilled with std rod piston combo is about 10.7.1 so how do you calcuate the 6 inch rod combo ?

[Trev Vaa 1,185]

whats the piston measurement down the bore? it wont change compression if comparing 0 deck to 0 deck.

 

standard 302 rods are just over 6" long, i think 6.030" center to center.

[CHESTNUTXE 7,304]

yes exactly,i just thought there was a different way to calcuate the short piston combo but its no different

[gerg 10,871]

Like XC said, if the gudgeon pin location is exactly 0.250" higher (for the 6.030" rod), the piston will sit exactly as it did with 5.78" rods and std pistons, so compression will be the same. I would gather though, that 10.7:1 on a long rod would be less prone to detonation and less sensitive to timing than a std setup due to longer dwell time.

[CHESTNUTXE 7,304]

so come on guys what is the correct comp for this combo approx 13.1 or 10.7 with 302 rods 351 crank and closed chamber std heads,we are getting many different figures ?

[gerg 10,871]

Here let me google that for you: http://www.wallaceracing.com/cr_test2.php<br /><br />Came up 11.47:1 on that calculator

[CHESTNUTXE 7,304]

i use the summit compression calcuator ,and by the same input i get 10.69.1 and by your one gerg i get 11.8 ? with same data input ?

[bear351c 10,270]

Pontiac..........not very reliable. 

[CHESTNUTXE 7,304]

baaaaaaaaaaaaaaaahhhhhhhaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

[gerg 10,871]

i use the summit compression calcuator ,and by the same input i get 10.69.1 and by your one gerg i get 11.8 ? with same data input ?

 

I went off zero deck, 58 cc, 0.041" head gasket, 3 cc valve reliefs, 3.5" stroke, 4.030" bore, 4.100 head gasket diameter. I guess it pays to use a few different ones to get it right

[CHESTNUTXE 7,304]

ok i used 0.040 head gasket diameter isnt that what it is 0.040 ? not 4.100 and 2cc valve

[CHESTNUTXE 7,304]

ahhhh you mean the outer diameter not thickness

[gerg 10,871]

Correctamundo... Big difference!

[CHESTNUTXE 7,304]

the summit one doesnt have the gasket diameter i wonder why

[CHESTNUTXE 7,304]

ok why the difference in gasket bore ? i see from 4.040 to 4.180 on MLS

[gerg 10,871]

Some aftermarket blocks use big bores, like 4.125" Dart, etc.

[CHESTNUTXE 7,304]

so what should i use on a 030  or 040 block